This invention relates to a prosthetic valve for non-invasive insertion in the vicinity of the lower esophagus sphincter (LES).
Gastroesophageal reflux is a physical condition in which stomach acids reflux, or flow back up from the stomach into the esophagus. Frequent reflux episodes (two or more times per week), results in a more severe problem known as gastroesophageal reflux disease (GERD). Gastroesophageal reflux disease is the most common form of dyspepsia, being present in approximately 40% of adults in the United States or an intermittent basis and some 10% on a daily basis. Dyspepsia or heartburn, is defined as a burning sensation or discomfort behind the breastbone or sternum and is the most common symptom of GERD. Other symptoms of gastroesophageal reflux disease include dysphasia, odynophagia, hemorrhage, water brash, and pulmonary manifestations such as asthma, coughing or intermittent wheezing due to acid aspiration. Dyspepsia also may mimic the symptoms of a myocardial infarction or severe angina pectoris.
Factors that are believed to cause GERD include: transient lower esophageal sphincter relaxations, decreased LES resting tone, delayed stomach emptying, and ineffective esophageal clearance. One primary cause of gastroesophageal reflux disease is the lack of competency of the lower esophageal sphincter. The lower esophageal sphincter or valve, is comprised of both smooth and skeletal muscle located at the gastroesophageal (GE) junction.
At rest, the LES maintains a high-pressure zone between 10 and 30 mm Hg above intragastric pressure. Upon deglutition, the LES relaxes before the esophagus contracts, allowing food to pass through into the stomach. After food passes into the stomach, the LES contracts to prevent the stomach contents and acids from regurgitating into the esophagus. The mechanism of the LES opening and closing is influenced by innervation via the vagus nerve and hormonal control of gastrin and possibly other gastrointestinal hormones.
Complications of GERD include esophageal erosion, esophageal ulcer, and esophageal stricture. Stricture formation often results from prolonged exposure of the esophageal mucosa to acid reflux. The most common clinical manifestation of stricture is dysphasia. Unlike dysphasia from non-strictured esophageal reflux, dysphasia caused by stricture is a progressive disorder in that the size of a bolus which can pass into the stomach progressively becomes smaller. Prolonged acid exposure to esophageal mucosa may lead to a more serious condition known as Barrett's esophagus. Barrett's esophagus is defined as the replacement of normal squamous epithelium with abnormal columnar epithelium. Barrett's esophagus or clinical change in tissue structure is clinically important not only as a marker of severe reflux, but also as a potential precursor to cancer of the esophagus.
Current methods of treating gastroesophageal reflux disease consist of life style changes such as weight loss and avoidance of certain foods that may exacerbate the symptoms of GERD. Avoidance of excessive bending combined with elevation of the head of the bed helps prevent nocturnal reflux. While avoidance of exacerbating factors may be helpful, there is relatively little data supporting the efficacy of lifestyle modification alone for the treatment of GERD. There are a variety of different techniques designed for the treatment of less serious cases of GERD. Medications have been used for years with varying results. Conventional antacids (TUMS.RTM., ROLAIDS.RTM.) produce short term relief, but often result in negative side effects including diarrhea and constipation. H2 blocker receptor antagonists (Cimetidine, Ranitidine) are relatively more effective in controlling symptoms than antacids, but result in treatment of the symptoms and not the underlying cause of the disease. The more powerful secretory inhibitors, the proton pump inhibitors (Omeprazole, Lansoprazole) are much more effective than H2 blockers, but are expensive and may, in the long term, produce negative side effects. The only alternative to these conventional forms of medical treatment, which must be taken constantly at great cost, are the surgical methods of preventing reflux.
There are numerous reflux operations available which perhaps reflect the inadequacy of any one procedure to totally control the problem. The most commonly performed operation, Nissen fundoplication, may be effective, but is often complicated by stricture formation or gas bloat syndrome. A laparoscopic Nissen approach has been developed, adding another dimension of difficulty, with long term results still in question. In addition, a percutaneous laparoscopic technique has been developed as can be seen, for example, in the U.S. Pat. No. 5,006,106 to Angelchik. Minimally invasive techniques, such as transesophageal implantation of a prosthetic valve have been attempted. See, for example, U.S. Pat. No. 4,846,836 to Reich. The existing forms of medical and surgical treatment for gastroesophageal reflux all have shortcomings.
In view of the foregoing, and notwithstanding the various efforts exemplified in the prior art, there remains a need for a non-invasive prosthetic valve and deployment methodology for transesophageal implantation into the vicinity of the lower esophageal sphincter. Preferably, the valve permits both antegrade and retrograde flow and is removable or replaceable with minimal trauma to the surrounding tissue.